Reservation handling in conjunction with switching between storage access protocols

ABSTRACT

At least one processing device is configured to register a logical storage device of a storage system for a first set of paths associated with a first access protocol using a host identifier, to send a first reservation command in the first access protocol over each of the paths in the first set of paths, to register the logical storage device of the storage system for a second set of paths associated with a second access protocol using the same host identifier used in registering the logical storage device for the first set of paths, to receive an additional reservation command in the first access protocol, and responsive to receipt of the additional reservation command in the first access protocol, to translate the additional reservation command to the second access protocol, and to send the additional reservation command in the second access protocol to the storage system.

FIELD

The field relates generally to information processing systems, and more particularly to storage in information processing systems.

BACKGROUND

Storage arrays and other types of storage systems are often shared by multiple host devices over a network. Applications running on the host devices each include one or more processes that perform the application functionality. The processes issue input-output (IO) operations directed to particular logical storage volumes or other logical storage devices, for delivery by the host devices over selected paths to storage ports of the storage system. Different ones of the host devices can run different applications with varying workloads and associated IO patterns. Such host devices also generate additional IO operations in performing various data services such as migration and replication. Various types of storage access protocols can be used by host devices to access the logical storage volumes or other logical storage devices of the storage system, including by way of example Small Computer System Interface (SCSI) access protocols and NVM Express (NVMe) access protocols. However, a given host device will typically be configured to utilize only one access protocol at a time to access a particular logical storage device, and reconfiguring such a host device to utilize a different access protocol to access that logical storage device can be problematic in some situations. For example, even though a storage system may support multiple access protocols like SCSI and NVMe for its logical storage devices, transforming host device access from SCSI to NVMe using conventional techniques can be problematic. As a more particular example, issues can arise in situations in which different host devices accessing a given logical storage device attempt to make reservations relating to that device using different access protocols. A need therefore exists for improved techniques that can avoid the drawbacks of conventional approaches.

SUMMARY

Illustrative embodiments provide techniques for reservation handling in heterogeneous storage access protocol environments involving at least first and second distinct access protocols. For example, one or more embodiments can seamlessly alter the particular access protocol through which a given logical storage volume or other logical storage device is accessed by one or more host devices, illustratively from a particular SCSI access protocol, such as SCSI over Fibre Channel (SCSI-FC), to a particular NVMe access protocol, such as NVMe over Fabrics (NVMeF), and vice versa, in a manner that provides consistent reservation handling across the multiple access protocols. It is to be appreciated that a wide variety of other types of storage access protocols can be used in other embodiments.

Some embodiments disclosed herein utilize a multi-path layer of one or more host devices in implementing reservation handling in conjunction with switching between the multiple access protocols, in a manner that provides enhanced access to the logical storage device and therefore improved overall system performance. For example, illustrative embodiments herein configure a multi-path layer to provide reservation handling functionality to support a clustered application across multiple protocols such that the management of reservations is independent of the particular storage access protocol used, thereby ensuring that the clustered application can switch between protocols seamlessly.

In one embodiment, an apparatus comprises at least one processing device comprising a processor and a memory coupled to the processor. The at least one processing device is configured to register a logical storage device of a storage system for a first set of paths associated with a first access protocol using a host identifier, to send a first reservation command in the first access protocol over each of the paths in the first set of paths, to register the logical storage device of the storage system for a second set of paths associated with a second access protocol using the same host identifier used in registering the logical storage device for the first set of paths, to receive an additional reservation command in the first access protocol, and responsive to receipt of the additional reservation command in the first access protocol, to translate the additional reservation command to the second access protocol, and to send the additional reservation command in the second access protocol to the storage system.

For example, in some embodiments, the at least one processing device is configured to switch the logical storage device from a SCSI access protocol such as SCSI-FC to an NVMe access protocol such as NVMeF, and vice versa, in a manner that maintains consistent reservation handling across the multiple access protocols.

The at least one processing device illustratively comprises at least a portion of at least one host device coupled to at least one storage array or other type of storage system via at least one network.

The paths in some embodiments are associated with respective initiator-target pairs, with each of a plurality of initiators of the initiator-target pairs comprising a corresponding host bus adaptor (HBA) of the at least one host device and each of a plurality of targets of the initiator-target pairs comprising a corresponding port of the storage system.

The at least one host device illustratively comprises a multi-path layer, with the multi-path layer comprising at least one multi-path input-output (MPIO) driver configured to control delivery of IO operations from the at least one host device to the storage system over selected paths through the network.

In some embodiments, the host identifier comprises a host name of a particular host device, such as a domain registered host name or a qualified name of the host device in accordance with a particular one of the access protocols. Other types of host names or host identifiers can be used in other embodiments.

In some embodiments, registering the logical storage device for the first set of paths associated with the first access protocol comprises, for each path in the first set of paths, sending a vendor unique registration command to the storage system for the path, and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the first access protocol. The storage system associates the host identifier with the registered keys for the respective paths of the first set of paths. For example, in the case of a SCSI access protocol, the key type specified in the first access protocol illustratively comprises a randomly-generated key. Other types of registration commands and keys can be used in other embodiments.

Additionally or alternatively, registering the logical storage device for the second set of paths associated with the second access protocol comprises, for each path in the second set of paths, sending a vendor unique registration command to the storage system for the path, and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the second access protocol. The storage system associates the host identifier with the registered keys for the respective paths of the second set of paths. For example, in the case of an NVMe access protocol, the key type specified in the second access protocol illustratively comprises a qualified name of the host device. This is an example of an arrangement in which the key type specified in the second access protocol comprises a host identifier. Again, other types of registration commands and keys can be used in other embodiments.

In some embodiments, the at least one processing device is further configured to send a vendor unique sense command to the storage system, and to receive multi-protocol configuration information from the storage system responsive to the vendor unique sense command. For example, the multi-protocol configuration information illustratively comprises one or more of (a) an indication as to whether or not multiple access protocols are supported by the storage system, and (b) an indication as to whether or not multiple access protocols reservations are supported by the storage system. The sense command may be, for example, a mode sense command or a log sense command, and like other commands referred to herein, may be a standard command instead of a vendor unique command.

In some embodiments, receiving an additional reservation command in the first access protocol comprises receiving a read reservation keys command.

Additionally or alternatively, the at least one processing device is further configured to receive from the storage system, in response to the additional reservation command sent to the storage system in the second access protocol, reservation information of a type specified in the second access protocol, and to provide the reservation information to a requesting application. Such reservation information illustratively comprises, for example, one or more reservation keys provided in response to a read reservation keys command.

These and other illustrative embodiments include, without limitation, apparatus, systems, methods and computer program products comprising processor-readable storage media.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an information processing system configured with functionality for multiple access protocol reservation handling utilizing a multi-path layer of a host device in an illustrative embodiment.

FIG. 2 is a flow diagram of a process for multiple access protocol reservation handling utilizing a multi-path layer of a host device in an illustrative embodiment.

FIG. 3 is a block diagram showing multiple layers of a layered system architecture that includes a multi-path layer with multiple access protocol reservation handling functionality in an illustrative embodiment.

FIG. 4 shows an example of multi-protocol reservation information in a registration database maintained by a storage array in an illustrative embodiment.

DETAILED DESCRIPTION

Illustrative embodiments will be described herein with reference to exemplary information processing systems and associated computers, servers, storage devices and other processing devices. It is to be appreciated, however, that these and other embodiments are not restricted to the particular illustrative system and device configurations shown. Accordingly, the term “information processing system” as used herein is intended to be broadly construed, so as to encompass, for example, processing systems comprising cloud computing and storage systems, as well as other types of processing systems comprising various combinations of physical and virtual processing resources. An information processing system may therefore comprise, for example, at least one data center or other cloud-based system that includes one or more clouds hosting multiple tenants that share cloud resources. Numerous different types of enterprise computing and storage systems are also encompassed by the term “information processing system” as that term is broadly used herein.

FIG. 1 shows an information processing system 100 configured in accordance with an illustrative embodiment. The information processing system 100 comprises at least first and second host devices 102-1 and 102-2, collectively referred to herein as host devices 102. The host devices 102 are coupled to a network 104 that comprises one or more switch fabrics. The host devices 102 communicate over the network 104 via the one or more switch fabrics with at least first and second storage arrays 105-1 and 105-2, collectively referred to herein as storage arrays 105. For example, the network 104 illustratively comprises at least one storage area network (SAN) and the one or more switch fabrics illustratively comprise respective distinct switch fabrics of a set of multiple switch fabrics interconnecting the host devices 102 with the storage arrays 105 over the one or more SANs. Each of the one or more switch fabrics in some embodiments is associated with a different SAN.

The system 100 may be configured such that the first host device 102-1 communicates with the first storage array 105-1 over a first switch fabric and communicates with the second storage array 105-2 over a second switch fabric. Similarly, the second host device 102-2 can communicate with the first storage array 105-1 over the first switch fabric and communicate with the second storage array 105-2 over the second switch fabric. Numerous other interconnection arrangements are possible.

Also, other types of networks can be used in other embodiments, and references to SANs, switch fabrics or other particular network arrangements herein are for purposes of illustration only, as non-limiting examples.

Although only two host devices 102 and two storage arrays 105 are shown in the figure, this is by way of illustrative example only, and other embodiments can include additional instances of such elements. It is also possible that alternative embodiments may include only a single host device.

The host devices 102 illustratively comprise respective computers, servers or other types of processing devices configured to communicate with the storage arrays 105 over the network 104. For example, at least a subset of the host devices 102 may be implemented as respective virtual machines of a compute services platform or other type of processing platform. The host devices 102 in such an arrangement illustratively provide compute services such as execution of one or more applications on behalf of each of one or more users associated with respective ones of the host devices 102. The term “user” herein is intended to be broadly construed so as to encompass numerous arrangements of human, hardware, software or firmware entities, as well as combinations of such entities.

Compute and/or storage services may be provided for users under a Platform-as-a-Service (PaaS) model, an Infrastructure-as-a-Service (IaaS) model and/or a Function-as-a-Service (FaaS) model, although it is to be appreciated that numerous other cloud infrastructure arrangements could be used. Also, illustrative embodiments can be implemented outside of the cloud infrastructure context, as in the case of a stand-alone computing and storage system implemented within a given enterprise.

The network 104 may be implemented using multiple networks of different types to interconnect the various components of the information processing system 100. For example, the network 104 may comprise a portion of a global computer network such as the Internet, although other types of networks can be part of the network 104, including a wide area network (WAN), a local area network (LAN), a satellite network, a telephone or cable network, a cellular network, a wireless network such as a WiFi or WiMAX network, or various portions or combinations of these and other types of networks. The network 104 in some embodiments therefore comprises combinations of multiple different types of networks each comprising processing devices configured to communicate using Internet Protocol (IP) and/or other types of communication protocols.

As a more particular example, some embodiments may utilize one or more high-speed local networks in which associated processing devices communicate with one another utilizing Peripheral Component Interconnect express (PCIe) cards of those devices, and networking protocols such as InfiniBand, Gigabit Ethernet or Fibre Channel. Numerous alternative networking arrangements are possible in a given embodiment, as will be appreciated by those skilled in the art.

Although illustratively shown as separate from the network 104 in the figure, at least portions of the storage arrays 105 may be considered part of the network 104 in some embodiments. For example, in embodiments in which the network 104 comprises at least one SAN, the storage arrays 105 may be viewed as part of the one or more SANs.

The storage arrays 105-1 and 105-2 comprise respective sets of storage devices 106-1 and 106-2, collectively referred to herein as storage devices 106, coupled to respective storage controllers 108-1 and 108-2, collectively referred to herein as storage controllers 108.

The storage devices 106 of the storage arrays 105 illustratively comprise solid state drives (SSDs). Such SSDs in some embodiments are implemented using non-volatile memory (NVM) devices such as flash memory. Other types of NVM devices that can be used to implement at least a portion of the storage devices 106 include non-volatile random access memory (NVRAM), phase-change RAM (PC-RAM), magnetic RAM (MRAM), resistive RAM, spin torque transfer magneto-resistive RAM (STT-MRAM), and Intel Optane™ devices based on 3D XPoint™ memory. These and various combinations of multiple different types of storage devices may also be used. For example, hard disk drives (HDDs) can be used in combination with or in place of SSDs or other types of NVM devices.

A given storage system as the term is broadly used herein can therefore include a combination of different types of storage devices, as in the case of a multi-tier storage system comprising, for example, a memory-based fast tier and a disk-based capacity tier. In such an embodiment, each of the fast tier and the capacity tier of the multi-tier storage system comprises a plurality of storage devices with different types of storage devices being used in different ones of the storage tiers. For example, the fast tier may comprise flash drives, NVM drives or other types of SSDs while the capacity tier comprises HDDs. The particular storage devices used in a given storage tier may be varied in other embodiments, and multiple distinct storage device types may be used within a single storage tier. The term “storage device” as used herein is intended to be broadly construed, so as to encompass, for example, SSDs, HDDs, flash drives, NVM drives, hybrid drives or other types of storage devices.

In some embodiments, at least one of the storage arrays 105 illustratively comprises one or more Unity™ or PowerMax™ storage arrays, commercially available from Dell Technologies. As another example, one or both of the storage arrays 105 may comprise respective clustered storage systems, each including a plurality of storage nodes interconnected by one or more networks. An example of a clustered storage system of this type is an XtremIO™ storage array from Dell Technologies, illustratively implemented in the form of a scale-out all-flash content addressable storage array.

A given storage system as the term is broadly used herein can additionally or alternatively comprise, for example, network-attached storage (NAS), direct-attached storage (DAS) and distributed DAS.

Other additional or alternative types of storage products that can be used in implementing a given storage system in illustrative embodiments include software-defined storage, cloud storage, object-based storage and scale-out storage. Combinations of multiple ones of these and other storage types can also be used in implementing a given storage system in an illustrative embodiment.

As mentioned above, communications between the host devices 102 and the storage arrays 105 within the system 100 may utilize PCIe connections or other types of connections implemented over one or more networks such as network 104. For example, illustrative embodiments can use interfaces such as Internet SCSI (iSCSI), Serial Attached SCSI (SAS) and Serial ATA (SATA). Numerous other interfaces and associated communication protocols can be used in other embodiments.

The storage arrays 105 in some embodiments may be implemented as part of cloud infrastructure in the form of a cloud-based system such as an Amazon Web Services (AWS) system. Other examples of cloud-based systems that can be used to provide at least portions of the storage arrays 105 and possibly other portions of system 100 include Google Cloud Platform (GCP) and Microsoft Azure.

As is apparent from the foregoing, terms such as “storage array” and “storage system” as used herein are intended to be broadly construed, and a given such storage array or storage system may encompass, for example, multiple distinct instances of a commercially-available storage array.

The storage devices 106 of the storage arrays 105 are configured to store data utilized by one or more applications running on one or more of the host devices 102. The storage devices 106 on one of the storage arrays 105 are illustratively arranged in one or more storage pools. The storage arrays 105 and their corresponding storage devices 106 are examples of what are more generally referred to herein as “storage systems.” A given such storage system in the present embodiment may be shared by the host devices 102, and in such arrangements may be referred to as a “shared storage system.”

The storage devices 106 of the storage arrays 105 implement logical units (LUNs) configured to store objects for users associated with the host devices 102. These objects can comprise files, blocks or other types of objects. The host devices 102 interact with the storage arrays 105 utilizing read and write commands as well as other types of commands that are transmitted over the network 104.

Such commands in some embodiments more particularly comprise SCSI commands, although other types of commands may be used in other embodiments, including commands that are part of a standard command set, or custom commands such as a “vendor unique command” or VU command that is not part of a standard command set. Such a “vendor unique command” as that term is broadly used herein illustratively comprises a command that is generally configured in accordance with a particular storage access protocol, but one or more features of the command are defined by an entity that manufactures, configures or otherwise provides a storage system to a customer or other user.

A given IO operation as that term is broadly used herein illustratively comprises one or more such commands. References herein to terms such as “input-output” and “IO” should be understood to refer to input and/or output. Thus, an IO operation relates to at least one of input and output. For example, an IO operation can comprise at least one read IO operation and/or at least one write IO operation. More particularly, IO operations may comprise write requests and/or read requests directed to stored data of a given one of the storage arrays 105.

Each IO operation is assumed to comprise one or more commands for instructing at least one of the storage arrays 105 to perform particular types of storage-related functions such as reading data from or writing data to particular logical storage volumes or other logical storage devices of one or more of the storage arrays 105. Such commands are assumed to have various payload sizes associated therewith, and the payload associated with a given command is referred to herein as its “command payload.”

A command directed by one of the host devices 102 to one of the storage arrays 105 is considered an “outstanding” command until such time as its execution is completed in the viewpoint of the sending host device, at which time it is considered a “completed” command. The commands illustratively comprise respective SCSI commands, although other command formats can be used in other embodiments. A given such command is illustratively defined by a corresponding command descriptor block (CDB) or similar format construct. The given command can have multiple blocks of payload associated therewith, such as a particular number of 512-byte SCSI blocks or other types of blocks.

Also, the term “storage device” as broadly used herein can encompass, for example, a logical storage device such as a LUN or other logical storage volume. A logical storage device can be defined in the storage arrays 105 to include different portions of one or more physical storage devices. The storage devices 106 may therefore be viewed as comprising respective LUNs or other logical storage volumes. Logical storage devices are also referred to herein as simply “logical devices.”

Each of the host devices 102 illustratively has multiple paths to each of the storage arrays 105 via the network 104, with at least one of the storage devices 106 of one of the storage arrays 105 being visible to that host device on a given one of the paths, although numerous other arrangements are possible. A given one of the storage devices 106 may be accessible to a given host device over multiple paths. Different ones of the host devices 102 can have different numbers and types of paths to the storage arrays 105.

Different ones of the storage devices 106 of the storage arrays 105 illustratively exhibit different latencies in processing of IO operations. In some cases, the same storage device may exhibit different latencies for different ones of multiple paths over which that storage device can be accessed from a given one of the host devices 102.

The host devices 102, network 104 and storage arrays 105 in the FIG. 1 embodiment are assumed to be implemented using at least one processing platform each comprising one or more processing devices each having a processor coupled to a memory. Such processing devices can illustratively include particular arrangements of compute, storage and network resources. For example, processing devices in some embodiments are implemented at least in part utilizing virtual resources such as virtual machines (VMs) or Linux containers (LXCs), or combinations of both as in an arrangement in which Docker containers or other types of LXCs are configured to run on VMs.

As a more particular example, the host devices 102 in some embodiments illustratively comprise an ESXi environment or other type of host environment that supports non-disruptive movement of applications between ESXi servers or other types of servers, possibly using vMotion or other similar techniques to move VMs, in which those application execute, from one server to another server.

Accordingly, in one or more embodiments, the host devices 102 are configured to support such application movement between those host devices. This application movement can be used as part of an automated seamless migration of a logical storage device between access protocols, although other types of automated seamless migration not involving application movement can be used in other embodiments. It should also be noted that application movement and automated seamless migration of logical storage devices are not utilized in some embodiments.

Additional examples of processing platforms utilized to implement storage systems and possibly one or more associated host devices in illustrative embodiments will be described in more detail below.

The host devices 102 and the storage arrays 105 may be implemented on respective distinct processing platforms, although numerous other arrangements are possible. For example, in some embodiments at least portions of the host devices 102 and the storage arrays 105 are implemented on the same processing platform. The storage arrays 105 can therefore be implemented at least in part within at least one processing platform that implements at least a subset of the host devices 102.

The term “processing platform” as used herein is intended to be broadly construed so as to encompass, by way of illustration and without limitation, multiple sets of processing devices and associated storage systems that are configured to communicate over one or more networks. For example, distributed implementations of the host devices 102 are possible, in which certain ones of the host devices 102 reside in one data center in a first geographic location while other ones of the host devices 102 reside in one or more other data centers in one or more other geographic locations that are potentially remote from the first geographic location. Thus, it is possible in some implementations of the system 100 for different ones of the host devices 102 to reside in different data centers than the storage arrays 105. The storage arrays 105 can be similarly distributed across multiple data centers.

Although in some embodiments certain commands used by the host devices 102 to communicate with the storage arrays 105 illustratively comprise SCSI commands, other types of commands and command formats can be used in other embodiments. For example, some embodiments can implement IO operations utilizing command features and functionality associated with NVM Express (NVMe), as described in the NVMe Specification, Revision 1.3, May 2017, which is incorporated by reference herein. Other storage protocols of this type that may be utilized in illustrative embodiments disclosed herein include NVMe over Fabrics, also referred to as NVMeF, and NVMe over Transmission Control Protocol (TCP), also referred to as NVMe/TCP.

The storage arrays 105-1 and 105-2 in some embodiments may be arranged in an active-active configuration, although use of such a configuration is not required. In an example of an active-active configuration that may be used, data stored in one of the storage arrays 105 is replicated to the other one of the storage arrays 105 utilizing a replication process. Such data replication across the multiple storage arrays 105 can be used to facilitate failure recovery in the system 100. One of the storage arrays 105 may therefore operate as a production storage array relative to the other storage array which operates as a backup or recovery storage array. Examples of active-active configurations include “metro” or “stretched” high availability storage array configurations. The term “active-active configuration” as used herein is therefore intended to be broadly construed.

The storage arrays 105-1 and 105-2 may be configured to participate in a replication process, such as a synchronous replication process. In accordance with one type of synchronous replication process, a given one of the host devices 102 writes data to one of the storage arrays 105, and that host device receives an acknowledgement of success only after the data has been successfully written to both of the storage arrays 105. For example, if the host device directs a write to the first storage array 105-1, that storage array mirrors the write to the second storage array 105-2 and receives an acknowledgement of success back from the second storage array 105-2. The first storage array 105-1 then responds back to the host device with an acknowledgement of success.

This type of synchronous replication process is therefore configured to mirror data writes from one or more of the host devices 102 to both of the storage arrays 105. Other types of replication processes may be used in other embodiments.

For example, a “replication process” as that term is broadly used herein may include both asynchronous and synchronous replication modes as well as support for concurrent operation of such modes and separate operation of the individual modes. It is also possible in some embodiments that a given replication process implemented using storage arrays 105 may comprise only synchronous replication or only asynchronous replication, instead of multiple distinct replication modes.

It is assumed that the storage controllers 108 of the respective storage arrays 105 each comprise replication control logic and a snapshot generator. The replication control logic controls performance of the above-noted replication process. The snapshot generator can be used, for example, to generate snapshots of one or more storage volumes that are subject to synchronous replication in conjunction with active-active storage clustering, and in a wide variety of different migration scenarios.

The snapshots generated by the storage controllers 108 of the storage arrays 105 illustratively comprise respective point-in-time (PIT) replicas of the storage volumes. Multiple snapshots generated over time for a given storage volume can collectively comprise a “snapshot group” and information characterizing those snapshots in some embodiments is stored in the form of a snapshot tree or other arrangement of one or more data structures suitable for storing information characterizing a snapshot group. In some embodiments, a snapshot tree for a storage volume is configured to add a new node each time a new snapshot is generated for that storage volume. The term “snapshot” as used herein is intended to be broadly construed, and in some embodiments may encompass a complete PIT replica or other types of information characterizing the state of a given storage volume at a particular time.

A given storage volume implemented on one or both of the storage arrays 105 in the system 100 illustratively comprises a set of one or more LUNs or other storage volumes of one or both of the storage arrays 105. Each such LUN or other storage volume is assumed to comprise at least a portion of a physical storage space of one or more of the storage devices 106 of the corresponding storage arrays 105.

The host devices 102 comprise respective sets of IO queues 110-1 and 110-2, and respective MPIO drivers 112-1 and 112-2. The MPIO drivers 112 collectively comprise a multi-path layer of the host devices 102. The multi-path layer provides automated path selection functionality using respective instances of path selection logic 114-1 and 114-2 implemented within the MPIO drivers 112.

In some embodiments, the multi-path layer additionally supports what is referred to herein as “multiple access protocol reservation handling” for logical storage devices of the storage arrays 105. Such multiple access protocol reservation handling functionality may be implemented at least in part in the multi-path layer, and may additionally or alternatively be implemented at least in part in one or more respective migration control logic instances of the host devices 102 and storage arrays 105.

The MPIO drivers 112 may comprise, for example, otherwise conventional MPIO drivers, such as PowerPath® drivers from Dell Technologies, suitably modified in the manner disclosed herein to support multiple access protocol reservation handling. Other types of MPIO drivers from other driver vendors may be suitably modified to incorporate functionality for multiple access protocol reservation handling as disclosed herein.

The MPIO driver 112-1 is configured to select IO operations from its corresponding set of IO queues 110-1 for delivery to the storage arrays 105 over the network 104. The sources of the IO operations stored in the set of IO queues 110-1 illustratively include respective processes of one or more applications executing on the host device 102-1. Other types of sources of IO operations may be present in a given implementation of system 100.

The paths over which the IO operations are sent from the host device 102-1 to the storage arrays 105 illustratively comprise paths associated with respective initiator-target pairs, with each initiator comprising a host bus adaptor (HBA) or other initiating entity of the host device 102-1 and each target comprising a storage array port or other targeted entity corresponding to one or more of the storage devices 106 of the storage arrays 105. As noted above, the storage devices 106 of the storage arrays 105 illustratively comprise LUNs or other types of logical storage devices.

For example, in selecting particular ones of the paths for delivery of the IO operations to the storage arrays 105, the path selection logic 114-1 of the MPIO driver 112-1 illustratively implements a path selection algorithm that selects particular ones of the paths at least in part as a function of path information such as host device HBA and storage array port, with the path selection algorithm being configured to balance the IO operations over the paths or to achieve other load balancing or performance goals.

Selecting a particular one of multiple available paths for delivery of a selected one of the IO operations of the set of IO queues 110-1 is more generally referred to herein as “path selection.” Path selection as that term is broadly used herein can in some cases involve both selection of a particular IO operation and selection of one of multiple possible paths for accessing a corresponding logical device of one of the storage arrays 105. The corresponding logical device illustratively comprises a LUN or other logical storage volume to which the particular IO operation is directed.

A given retry of a failed IO operation under such a path selection algorithm can select a path having a different host device HBA and storage array port for a given retry than that of the path selected for the original failed IO operation.

The paths between the host devices 102 and the storage arrays 105 can change over time. For example, the addition of one or more new paths from host device 102-1 to the storage arrays 105 or the deletion of one or more existing paths from the host device 102-1 to the storage arrays 105 may result from respective addition or deletion of at least a portion of the storage devices 106 of the storage arrays 105. Addition or deletion of paths can also occur as a result of zoning and masking changes or other types of storage system reconfigurations performed by a storage administrator or other user.

In some embodiments, paths are added or deleted in conjunction with addition of a new storage array or deletion of an existing storage array from a storage system that includes multiple storage arrays, possibly in conjunction with configuration of the storage system for at least one of a migration operation and a replication operation.

In these and other situations, path discovery scans may be repeated as needed in order to discover the addition of new paths or the deletion of existing paths.

A given path discovery scan can be performed utilizing known functionality of conventional MPIO drivers, such as PowerPath® drivers.

The path discovery scan in some embodiments may be further configured to identify one or more new LUNs or other logical storage volumes associated with the one or more new paths identified in the path discovery scan. The path discovery scan may comprise, for example, one or more bus scans which are configured to discover the appearance of any new LUNs that have been added to the storage arrays 105 as well to discover the disappearance of any existing LUNs that have been deleted from the storage arrays 105.

The MPIO driver 112-1 in some embodiments comprises a user-space portion and a kernel-space portion. The kernel-space portion of the MPIO driver 112-1 may be configured to detect one or more path changes of the type mentioned above, and to instruct the user-space portion of the MPIO driver 112-1 to run a path discovery scan responsive to the detected path changes. Other divisions of functionality between the user-space portion and the kernel-space portion of the MPIO driver 112-1 are possible.

For each of one or more new paths identified in the path discovery scan, the host device 102-1 may be configured to execute a host registration operation for that path. The host registration operation for a given new path illustratively provides notification to the corresponding one of the storage arrays 105 that the host device 102-1 has discovered the new path.

As is apparent from the foregoing, MPIO driver 112-1 of host device 102-1 is configured to control delivery of IO operations from the host device 102-1 to the first and second storage arrays 105 over selected paths through the network 104.

The MPIO driver 112-1 is also configured to implement at least portions of multiple access protocol reservation handling functionality of host device 102-1. Other host device components, such as migration control logic implemented in one or more host device processors, can additionally or alternatively implement aspects of the multiple access protocol reservation handling functionality of the host device 102-1. The disclosed embodiments are therefore not limited to embodiments in which multiple access protocol reservation handling functionality is controlled at least in part by an MPIO driver or multi-path layer.

As indicated previously, migration of logical storage volumes or other logical storage devices across multiple access protocols can be problematic. For example, host-based seamless migration in these and other contexts can be inefficient, consuming significant amounts of computational and network resources of the host device. Such requirements of conventional approaches can negatively impact the seamless migration process and thereby degrade overall system performance.

For example, some conventional host-based migration processes such as PowerPath® Migration Enabler (PPME) typically require that a host administrator and a storage administrator cooperate in setting up and executing the migration process, which in some circumstances can complicate the migration effort.

Storage-based migration processes such as Non-Destructive Migration (NDM) of a source device to a target device, which may be on the same storage array or on respective different source and target storage arrays, do not require such cooperation, but typically require device spoofing. More particularly, these storage-based migration processes typically require the target device to spoof the source device identifier or ID. This spoofing poses problems since the target device ID on the target array in some cases does not reflect the actual storage array on which the device resides, in situations in which the source and target devices are on different storage arrays. For example, if the storage array information is embedded in the device ID, and the target device is spoofing the source device by using the source device ID, the storage array information embedded in the spoofed device ID will indicate the source array and not the target array, even though the target device is located on the target array.

Host-based migration processes such as the above-noted PPME allow the target device to keep its own device ID, as an MPIO driver of a multi-path layer can merge the two device IDs into a single device ID for presentation to a host device processor layer, thereby avoiding the problems associated with spoofing.

The multiple access protocol reservation handling techniques of illustrative embodiments disclosed herein provide significant advantages over these and other conventional approaches.

For example, some embodiments are configured to facilitate migration of a logical storage device from use of a first access protocol such as SCSI-FC to use of second access protocol such as NVMeF, and vice versa, in a particularly efficient manner that intelligently leverages multi-pathing functionality of a given host device environment to maintain consistent reservation handling across the first and second access protocols. Such multiple access protocol reservation handling can be implemented across two or more distinct access protocols of numerous other types in other embodiments.

In accordance with the multiple access protocol reservation handling functionality of illustrative embodiments, an MPIO layer comprising one or more of the MPIO drivers 112-1 and 112-2 of the respective host devices 102-1 and 102-2 is configured to switch the at least one logical storage device from utilization of a first access protocol to utilization of a second access protocol different than the first access protocol while maintaining consistent reservation handling across the multiple access protocols.

For example, the MPIO layer comprising at least one of the MPIO drivers 112 is illustratively configured to register a logical storage device of a given one of the storage arrays 105 for a first set of paths associated with a first access protocol using a host identifier. The MPIO layer is further configured to send a first reservation command in the first access protocol over each of the paths in the first set of paths, to register the logical storage device of the storage array for a second set of paths associated with a second access protocol using the same host identifier used in registering the logical storage device for the first set of paths, to receive an additional reservation command in the first access protocol, and responsive to receipt of the additional reservation command in the first access protocol, to translate the additional reservation command to the second access protocol, and to send the additional reservation command in the second access protocol to the storage array.

Such an MPIO layer illustratively runs on at least one processing device that comprises at least a portion of at least one of the host devices 102 coupled to the storage arrays 105 via the network 104. Other arrangements of one or more processing devices, each comprising at least one processor and at least one memory coupled to the at least one processor, may be used in other embodiments.

An information processing system environment such as that described above, in which one or more hosts access logical storage devices of at least one storage system using at least first and second distinct access protocols, is an example of what is more generally referred to herein as a “heterogeneous storage access protocol environment.”

As indicated previously, the first and second access protocols illustratively comprise respective SCSI and NVMe access protocols, such as SCSI-FC and NVMeF access protocols, although other arrangements of two or more distinct access protocols can be used in other embodiments.

In some embodiments, the paths are associated with respective initiator-target pairs, with each of a plurality of initiators of the initiator-target pairs comprising an HBA of one of the host devices 102 and each of a plurality of targets of the initiator-target pairs comprising a corresponding port of one of the storage arrays 105.

In some embodiments, the above-noted host identifier used in registering the logical storage device for both the first and second sets of paths comprises a host name of a particular host device, such as a domain registered host name or a qualified name of the host device in accordance with a particular one of the access protocols. Other types of host names or host identifiers can be used in other embodiments. The same host identifier is used in illustrative embodiments to register the logical storage device for paths associated with the first access protocol and for paths associated with the second access protocol.

In some embodiments, registering the logical storage device for the first set of paths associated with the first access protocol comprises, for each path in the first set of paths, sending a VU registration command to the storage array for the path, and sending a registered key for the path with the vendor unique registration command, with the registered key having a key type specified in the first access protocol. The storage array associates the host identifier with the registered keys for the respective paths of the first set of paths. For example, in the case of a SCSI access protocol, the key type specified in the first access protocol illustratively comprises a randomly-generated key. It is to be appreciated that use of a VU registration command is not required, and other embodiments can use different arrangements of registration commands and associated keys.

Additionally or alternatively, registering the logical storage device for the second set of paths associated with the second access protocol comprises, for each path in the second set of paths, sending a VU registration command to the storage array for the path, and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the second access protocol. The storage array associates the host identifier with the registered keys for the respective paths of the second set of paths. For example, in the case of an NVMe access protocol, the key type specified in the second access protocol illustratively comprises a qualified name of the host device. This is an example of an arrangement in which the key type specified in the second access protocol comprises a host identifier. Again, it is to be appreciated that use of a VU registration command is not required, and other embodiments can use different arrangements of registration commands and associated keys.

In some embodiments, the MPIO layer is further configured to send a VU sense command to the storage array, and to receive multi-protocol configuration information from the storage array responsive to the VU sense command. For example, the multi-protocol configuration information illustratively comprises one or more of (a) an indication as to whether or not multiple access protocols are supported by the storage array, and (b) an indication as to whether or not multiple access protocols reservations are supported by the storage array. The sense command may be, for example, a mode sense command or a log sense command. As with other commands mentioned in the context of illustrative embodiments herein, use of VU commands is not required, and alternative embodiments can therefore use standard commands.

In some embodiments, receiving an additional reservation command in the first access protocol comprises receiving a read reservation keys command.

Additionally or alternatively, the at least one processing device is further configured to receive from the storage array, in response to the additional reservation command sent to the storage array in the second access protocol, reservation information of a type specified in the second access protocol, and to provide the reservation information to a requesting application. Such reservation information illustratively comprises, for example, one or more reservation keys provided in response to a read reservation keys command.

In illustrative embodiments, different access protocols are utilized to access the logical storage device at different times, while maintaining consistent reservation handling across the multiple access protocols.

Accordingly, at least one of the MPIO drivers 112 of at least one of the host devices 102 is configured to dynamically switch the logical storage device between utilization of the first and second access protocols over a plurality of access protocol switching instances, while maintaining consistent reservation handling across the multiple access protocols.

In some embodiments, the host device operating system (OS) may be unaware of the fact that the MPIO layer has switched the access protocol used to access the logical storage device. The MPIO layer in such an arrangement “hides” the access protocol switching from one or more higher layers of the host device.

These or other similar operations can additionally or alternatively be performed by interaction between the MPIO driver 112-1 and the second storage array 105-2, interaction between the MPIO driver 112-2 and the second storage array 105-2, and/or interaction between the MPIO driver 112-2 and the first storage array 105-1.

Via the operation of the MPIO layer in illustrative embodiments described above, both of the host devices 102-1 and 102-2 can illustratively switch between accessing the logical storage device using the first access protocol and accessing the logical storage device using the second access protocol.

In some embodiments, in conjunction with switching the logical storage device from utilization of the first access protocol to utilization of the second access protocol or vice versa, at least one of the MPIO drivers 112 of at least one of the host devices 102 may be configured to temporarily pause sending of IO operations to the logical storage device, to allow one or more IO operations previously sent to the logical storage device to complete, to switch the logical storage device between access protocols, and responsive to completion of the switch between access protocols, to resume sending of IO operations to the logical storage device. Such pausing and resuming is not required in other embodiments.

In some embodiments, the above-noted switching between access protocols, in a manner that maintains consistent reservation handling across the multiple access protocols, utilizes automated seamless migration of a logical storage device from one access protocol to another, and vice versa. Examples of automated seamless migration techniques that may be used in some embodiments herein are disclosed in U.S. patent application Ser. No. 17/106,788, filed Nov. 30, 2020 and entitled “Automated Seamless Migration across Access Protocols for a Logical Storage Device,” and U.S. patent application Ser. No. 16/797,671, filed Feb. 21, 2020 and entitled “Host Device with Efficient Automated Seamless Migration of Logical Storage Devices across Multiple Access Protocols,” each incorporated by reference herein in its entirety. It is to be appreciated, however, that such automated seamless migration techniques are not required, however, and other types of switching between access protocols for one or more logical storage devices can be used in other embodiments.

Illustrative embodiments implementing “automated seamless migration” of logical storage devices are “automated” in that no coordination between a host administrator and a storage administrator is required, and are also “seamless” in that each host device seamlessly transitions from usage of the first access protocol to usage of the second access protocol to access the logical storage device, and vice versa, illustratively without disrupting the operation of applications that utilize that logical storage device. Other advantages are provided by other automated seamless migration arrangements in other embodiments.

Terms such as “migrate” and “migration” as used herein are intended to be broadly construed, so as to encompass, for example, reconfiguring or otherwise transitioning a logical storage device and/or one or more associated host devices from utilization of a first access protocol to utilization of a second access protocol. Alternative access protocol switching arrangements can be used in other embodiments.

In some embodiments, the multi-path layer receives an access protocol change notification, which initiates the process of switching the logical storage device from utilization of the first access protocol to utilization of the second access protocol. The access protocol change notification in some embodiments comprises a check condition notification received from one of the storage arrays 105 that includes the logical storage device, and/or at least one command entered by an administrator or other user via a command line interface (CLI) or other user interface of at least one of the host devices 102.

In some embodiments, switching between access protocols is illustratively implemented using a process in which one or more hosts previously accessing a logical storage device via a particular one of the access protocols are reconfigured to access the logical storage device via the other one of the access protocols. In some arrangements of this type, it is assumed that the host OS is unable to access the logical storage device using the first and second access protocols simultaneously, and can instead only access the logical storage device using one of the access protocols at any given time.

Accordingly, some embodiments herein configure an MPIO layer to migrate, swap or otherwise switch at least one host from its currently used access protocol for the logical storage device to the other access protocol. Such dynamic switching between access protocols illustratively leverages the MPIO layer to provide consistent reservation handling between utilization of different access protocols for one or more logical storage devices.

It should be noted that references in the above description and elsewhere herein to migration, swapping or other types of switching of single logical storage devices across multiple access protocols are non-limiting, and other embodiments can simultaneously migrate, swap or otherwise switch multiple logical storage devices across multiple access protocols, through straightforward modification of the techniques disclosed herein, as will be readily apparent to those skilled in the art.

Such embodiments advantageously provide enhanced system performance by dynamically switching between SCSI-FC and NVMeF access protocols, and vice versa, or between other arrangements of multiple access protocols, for each of one or more logical storage devices of the system 100. For example, some existing HBAs support both multiple access protocols, such as SCSI-FC and NVMeF modes, so in systems with such HBAs there is no need to change hardware in order to migrate, swap or otherwise switch logical storage devices between the two different access protocols. However, as indicated previously, conventional techniques in these and other contexts generally do not permit host devices to dynamically switch a logical storage device between multiple access protocols in a manner that maintains consistent reservation handling across the multiple access protocols.

The above-described functions associated with multiple access protocol reservation handling functionality of the host device 102-1 are illustratively carried out at least in part utilizing the MPIO driver 112-1 and its path selection logic 114-1. For example, in some embodiments, the reservation handling functionality can be implemented substantially entirely under the control of the MPIO driver 112-1, and in such embodiments the path selection logic 114-1 is illustratively configured to control performance of one or more steps of the flow diagram to be described below in conjunction with FIG. 2.

Additional or alternative host device components, such as migration control logic implemented in the host device, can be used to control performance of a multiple access protocol reservation handling process such as that of FIG. 2.

It is assumed that the other MPIO driver 112-2 is configured in a manner similar to that described above and elsewhere herein for the first MPIO driver 112-1. The MPIO driver 112-2 is therefore similarly configured to select IO operations from its corresponding one of the sets of I0 queues 110 for delivery to the storage arrays 105 over the network 104 and to perform at least portions of the disclosed multiple access protocol reservation handling functionality. Accordingly, aspects of multiple access protocol reservation handling functionality described above in the context of the first MPIO driver 112-1 and the first host device 102-1 are assumed to be similarly performed by the other MPIO driver 112-2 and the other host device 102-2.

The MPIO drivers 112 may be otherwise configured utilizing well-known MPIO functionality such as that described in “Dell EMC SC Series Storage and Microsoft Multipath I/O,” Dell EMC, CML1004, July 2018, which is incorporated by reference herein. Such conventional MPIO functionality is suitably modified in illustrative embodiments disclosed herein to support multiple access protocol reservation handling.

It is to be appreciated that the above-described features of system 100 and other features of other illustrative embodiments are presented by way of example only, and should not be construed as limiting in any way. Accordingly, different numbers, types and arrangements of system components such as host devices 102, network 104, storage arrays 105, storage devices 106, sets of IO queues 110, MPIO drivers 112 and instances of path selection logic 114 can be used in other embodiments.

It should also be understood that the particular sets of modules and other components implemented in the system 100 as illustrated in FIG. 1 are presented by way of example only. In other embodiments, only subsets of these components, or additional or alternative sets of components, may be used, and such components may exhibit alternative functionality and configurations. For example, as indicated previously, instances of migration control logic implemented in the host devices 102 and the storage arrays 105 can be used to perform at least portions of the multiple access protocol reservation handling functionality.

The operation of the information processing system 100 will now be described in further detail with reference to the flow diagram of the illustrative embodiment of FIG. 2. The process as shown includes steps 200 through 210, and is suitable for use in the system 100 but is more generally applicable to other types of systems comprising one or more host devices and at least one storage system. The one or more host devices are illustratively the first and second host devices 102-1 and 102-2 of FIG. 1, and the storage system illustratively comprises one or both of the storage arrays 105, with each such storage array comprising a plurality of storage devices. The storage devices of each such storage array are assumed to include logical storage devices such as LUNs or other logical storage volumes.

The steps of the FIG. 2 process are illustratively performed primarily by or under the control of an MPIO layer comprising one or more MPIO drivers of respective host devices, such as the MPIO drivers 112-1 and 112-2 of the first and second host devices 102-1 and 102-2 of system 100, although other arrangements of system components can perform at least portions of one or more of the steps in other embodiments. At least portions of the functionality of the FIG. 2 process may be performed at least in part in conjunction with a load balancing algorithm or other type of path selection algorithm executed by instances of path selection logic 114 of one or more MPIO drivers 112. A given host device is referred to as simply a “host” in the FIG. 2 process and elsewhere herein.

In step 200, the MPIO driver of the given host device registers a logical storage device of a storage array for a first set of paths associated with a first access protocol, using a particular host identifier. For example, the host identifier illustratively comprises a host name of a particular host device, such as a domain registered host name or a qualified name of the host device in accordance with a particular one of the access protocols. Other types of host names or host identifiers can be used in other embodiments.

It is assumed in the present embodiment that one or more hosts are each configured to access the logical storage device using the first access protocol, illustratively a SCSI access protocol. The FIG. 2 process illustratively involves migrating, swapping or otherwise switching the logical storage device from utilization of the SCSI access protocol to utilization of another access protocol, illustratively an NVMe access protocol, and vice versa, while maintaining consistent reservation handling across the multiple access protocols. The SCSI and NVMe protocols utilized in the present embodiment are examples of what are more generally referred to herein as “first and second access protocols.”

The SCSI and NVMe protocols may more particularly comprise SCSI-FC and NVMeF access protocols, respectively, although numerous other types of first and second access protocols can be used in other embodiments. The logical storage device illustratively comprises a LUN or other type of logical storage volume implemented using storage devices of one or more of the storage arrays 105.

In step 202, the MPIO driver sends a first reservation command in the first access protocol over each path in the first set of paths. For example, the first reservation command may comprise a SCSI Persistent Reserve Out (PRO) command. Other types of reservation commands, in a SCSI access protocol or in other access protocols, may be used.

In step 204, the MPIO driver registers the logical storage device for a second set of paths associated with the second access protocol, using the same host identifier that was used in step 200 to register the logical storage device for the first set of paths.

In step 206, a determination is made, by the MPIO driver, as to whether or not an additional reservation command is received in the first access protocol. For example, the additional reservation command may comprise a SCSI Persistent Reserve In (PRI) command, utilized to read reservation keys from the storage array. Other types of reservation commands, in a SCSI access protocol or in other access protocols, may be used. If the additional reservation command is received, the process moves to step 208, and otherwise returns to step 206 as indicated.

In step 208, the MPIO driver translates the additional reservation command from the first access protocol to the second access protocol. For example, the MPIO illustratively translates a SCSI reservation command to corresponding an NVMe reservation command.

In step 210, the MPIO driver sends the translated additional reservation command in the second access protocol to the storage array. The process then returns to step 206 to handle other additional reservation commands that may be received.

The above-described process illustratively switches the host from accessing the logical storage device via the first access protocol to accessing the logical storage device via the second access protocol, in a seamless manner that is transparent to one or more applications that execute on the host and that utilize the logical storage device. Similar steps can be used to switch the host back from the second access protocol back to the first access protocol can be achieved if needed, in a straightforward manner.

Moreover, the process can be executed at least in part in parallel on multiple hosts in order to switch each of the hosts from accessing the logical storage device via the first access protocol to accessing the logical storage device via the second access protocol, in a seamless manner that is transparent to applications that execute on respective ones of the multiple hosts and that utilize the logical storage device. In some embodiments of this type, the storage array can facilitate the coordination of switching between access protocols on different host devices used to execute a clustered application, illustratively by sending a check condition notification or other type of notification to MPIO drivers on respective ones of the host devices, so that an MPIO layer comprising the MPIO drivers can coordinate the switching between access protocols on each of the host devices. Other types of access protocol change notifications can be used to facilitate such coordinated switching between access protocols.

The steps of the FIG. 2 process are shown in sequential order for clarity and simplicity of illustration only, and certain steps can at least partially overlap with other steps. Also, one or more of the steps referred to as being performed by a particular system component, such as an MPIO driver, can in other embodiments be performed at least in part by one or more other system components.

As indicated above, different instances of the FIG. 2 process can execute at least in part in parallel with one another for different logical storage devices. Also, multiple additional instances of the FIG. 2 process can be performed in respective ones of one or more additional host devices that access the logical storage device, by one or more MPIO drivers implemented on the one or more additional host devices.

The particular processing operations and other system functionality described in conjunction with the flow diagram of FIG. 2 are presented by way of illustrative example only, and should not be construed as limiting the scope of the disclosure in any way. Alternative embodiments can use other types of processing operations involving host devices, storage systems and multiple access protocol reservation handling functionality. For example, the ordering of the process steps may be varied in other embodiments, or certain steps may be performed at least in part concurrently with one another rather than serially. Also, one or more of the process steps may be repeated periodically, or multiple instances of the process can be performed in parallel with one another in order to implement a plurality of different multiple access protocol reservation handling arrangements within a given information processing system.

Functionality such as that described in conjunction with the flow diagram of FIG. 2 can be implemented at least in part in the form of one or more software programs stored in memory and executed by a processor of a processing device such as a computer or server. As will be described below, a memory or other storage device having executable program code of one or more software programs embodied therein is an example of what is more generally referred to herein as a “processor-readable storage medium.”

Referring now to FIG. 3, another illustrative embodiment is shown. In this embodiment, an information processing system 300 comprises host-side migration control logic 311, reservation information 312, path selection logic 314 and storage-side migration control logic 321. The system 300 is configured in accordance with a layered system architecture that illustratively includes a host device processor layer 330, an MPIO layer 332, an HBA layer 334, a switch fabric layer 336, a storage array port layer 338 and a storage array processor layer 340. As illustrated in the figure, the host device processor layer 330, the MPIO layer 332 and the HBA layer 334 are associated with one or more host devices, the switch fabric layer 336 is associated with one or more SANs or other types of networks, and the storage array port layer 338 and storage array processor layer 340 are associated with one or more storage arrays (“SAs”).

The system 300 in this embodiment implements multiple access protocol reservation handling for each of one or more logical storage volumes or other logical storage devices of one or more storage arrays. The logical storage devices store data for one or more application processes running in one or more host device processors of the host device processor layer 330. The multiple access protocol reservation handling functionality in this embodiment is assumed to be controlled at least in part by path selection logic 314 of the MPIO layer 332, utilizing reservation information 312, although other arrangements are possible.

In illustrative embodiments that involve use of at least one of host-side migration control logic 311 and storage-side migration control logic 321, automated seamless migration functionality can be implemented at least in part using these components. Accordingly, in some embodiments, the host-side and storage-side migration control logic 311 and 321 are illustratively configured to implement at least portions of the functionality for multiple access protocol reservation handling as disclosed herein. Other embodiments do not use automated seamless migration.

The host-side migration control logic 311 implemented in the host processor layer 330 controls host-based migration processes of the system 300. The migration control logic 311 can include multiple distinct migration control logic instances for respective ones of a plurality of host devices of the system 300.

The storage-side migration control logic 321 implemented in the storage array processor layer 340 controls storage-based migration processes of the system 300. The migration control logic 321 can include multiple distinct migration control logic instances for respective ones of a plurality of storage arrays of the system 300.

These components are shown in dashed outline in the figure, as they can be implemented in different locations within the system 300, or in a distributed manner across multiple locations. For example, the host-side migration control logic 311, although illustratively shown as part of the host processor layer 330, can be implemented at least in part in the MPIO layer 332. As another example, the storage-side migration control logic 321, although illustratively shown as part of the storage array processor layer 340, can be implemented at least in part in the storage array port layer 338. The reservation information 312 is also shown in dashed outline, as it can be implemented at least in part in different locations within the system 300, such as within MPIO layer 332, or in a distributed manner across multiple locations.

The MPIO layer 332 is an example of what is also referred to herein as a multi-path layer, and comprises one or more MPIO drivers implemented in respective host devices. Each such MPIO driver illustratively comprises an instance of path selection logic 314 configured to perform path selection for delivery of IO operations to the storage arrays of system 300 as previously described. The path selection logic 314 in some embodiments is configured, possibly in conjunction with the host-side and storage-side migration control logic 311 and 321, to implement at least portions of the functionality for multiple access protocol reservation handling as disclosed herein. Additional or alternative layers and path selection logic arrangements can be used in other embodiments.

In the system 300, path selection logic 314 is configured to select different paths for sending IO operations from a given host device to a storage array. These paths as illustrated in the figure include a first path from a particular HBA denoted HBA1 through a particular switch fabric denoted SF1 to a particular storage array port denoted PORT1, and a second path from another particular HBA denoted HBA2 through another particular switch fabric denoted SF2 to another particular storage array port denoted PORT2.

These two particular paths are shown by way of illustrative example only, and in many practical implementations there will typically be a much larger number of paths between the one or more host devices and the one or more storage arrays, depending upon the specific system configuration and its deployed numbers of HBAs, switch fabrics and storage array ports. For example, each host device in the FIG. 3 embodiment can illustratively have a set of n paths to a shared storage array, or alternatively different ones of the host devices can have different numbers and types of paths to the storage array.

The path selection logic 314 of the MPIO layer 332 in this embodiment therefore selects paths for delivery of IO operations to the one or more storage arrays having the storage array ports of the storage array port layer 338.

In some embodiments, the host devices and storage arrays of system 300 through their respective instances of migration control logic 311 or 321 provide functionality for automated seamless migration across multiple access protocols as described elsewhere herein, possibly with involvement of other host device or system components, such as the path selection logic 314 of MPIO layer 332. Such automated seamless migration can be used in some embodiments in conjunction with switching a logical storage device between access protocols, but again, automated seamless migration is not required.

Some implementations of the system 300 can include a relatively large number of host devices (e.g., 1000 or more host devices), although as indicated previously different numbers of host devices, and possibly only a single host device, may be present in other embodiments. Each of the host devices is typically allocated with a sufficient number of HBAs to accommodate predicted performance needs. In some cases, the number of HBAs per host device is on the order of 4, 8 or 16 HBAs, although other numbers of HBAs could be allocated to each host device depending upon the predicted performance needs. A typical storage array may include on the order of 128 ports, although again other numbers can be used based on the particular needs of the implementation. The number of host devices per storage array port in some cases can be on the order of 10 host devices per port. The HBAs of the host devices are assumed to be zoned and masked to the storage array ports in accordance with the predicted performance needs, including user load predictions.

A given host device of system 300 can be configured to initiate an automated path discovery process to discover new paths responsive to updated zoning and masking or other types of storage system reconfigurations performed by a storage administrator or other user. For certain types of host devices, such as host devices using particular operating systems such as Windows, ESX or Linux, automated path discovery via the MPIO drivers of a multi-path layer is typically supported. Other types of host devices using other operating systems such as AIX in some implementations do not necessarily support such automated path discovery, in which case alternative techniques can be used to discover paths.

Additional illustrative embodiments will now be described. It is assumed in these embodiments that the MPIO driver of a given host device provides the disclosed functionality for multiple access protocol reservation handling, utilizing a corresponding instance of path selection logic implemented in the MPIO driver, possibly with involvement of one or more other host device components.

FIG. 4 shows an example of multi-protocol reservation information 400 in a registration database maintained by a storage array, such as one of the storage arrays 105 in the FIG. 1 embodiment, or one of the storage arrays of the system 300 in the FIG. 3 embodiment. The example multi-protocol reservation information 400 in this embodiment is illustratively maintained in the form of a table, and comprises at least a portion of the registration database maintained by the storage array, although other types of data structures and registration information storage arrangements can be used in other embodiments. At least portions of such information is illustratively determined by the MPIO layer of the host device and communicated to the storage array.

In the context of the FIG. 1 embodiment, at least portions of the multi-protocol reservation information 400 are illustratively provided to the storage array by a given one of the MPIO drivers 112 of one of the host devices 102 and stored by the storage array in one or more tables or other data structures in at least one memory associated with one or more of the storage array processors of the storage array.

In the context of the FIG. 3 embodiment, the multi-protocol reservation information 400 includes at least portions of the reservation information 312, and is illustratively provided by an MPIO layer 332 to the storage array via the storage array layers 338 and 340, and stored in one or more tables or other data structures in at least one memory associated with one or more of the processors of host device processors layer 330.

The multi-protocol reservation information 400 more particularly comprises a plurality of entries for different ones of the paths to the storage array, with each such entry comprising a path identifier and reservation information for that path. Different ones of the paths are associated with different ones of first and second access protocols, such as respective SCSI-FC and NVMeF access protocols, utilized by a particular host device, denoted as Host 1, to access a particular logical storage device. It is assumed that similar multi-protocol reservation information is maintained by the storage array for other logical storage devices, and for other host devices that access those logical storage devices using one or more access protocols, illustratively in other portions of the registration database.

The paths associated with the first access protocol in Host 1 are denoted in the figure as Path 1-1, Path 1-2, . . . Path 1-J, and have their respective identifiers entered in a first column of the table of FIG. 4. Similarly, the paths associated with the second access protocol in Host 1 are denoted in the figure as Path 2-1, Path 2-2, . . . Path 2-K, and also have their respective identifiers entered in the first column of the table of FIG. 4. The second column of the table includes a common host name utilized by the MPIO layer of Host 1 in registering the first and second sets of paths for the logical storage device in association with respective first and second access protocols. The third column includes one or more associated keys, such as registered keys, reservation keys and/or other keys, for each of the registered paths to the logical storage device under both first and second access protocols. Examples of such keys are described in more detail in the SCSI and NVMe access protocol specifications. Terms such as “key” and “keys” as used herein are intended to be broadly construed, and should not be viewed as being limited to any particular key types of particular access protocols.

In this embodiment, the multi-protocol registration information is configured as a “merged” registration table that combines registration information for different paths associated with different access protocols for a given logical storage device, in this case by associating each of the paths with the common host name.

Numerous other types and arrangements of entries and fields can be used, and the term “multi-protocol reservation information” as used herein is therefore intended to be broadly construed. For example, different tables or other data structures may be used for different path sets associated with different access protocols.

Although FIG. 4 illustrates multi-protocol reservation information 400 as maintained in a registration database of a storage array, at least portions of such registration information can additionally be stored in one or more data structures of a multi-path layer of the host device and/or in other data structures elsewhere in the host device.

Another additional embodiment implements a process that is illustratively performed by an MPIO layer, possibly in cooperation with other host device components. Such an embodiment can be configured, for example, to switch the logical storage device from utilization of one access protocol to utilization of another access protocol, in a manner that maintains consistent reservation handling across the multiple access protocols.

The process in the present example more particularly comprises an algorithm performed by at least one host device interacting with at least one storage array, with the one or more host devices illustratively utilizing their respective MPIO drivers to perform at least portions of the algorithm. For example, the algorithm is illustratively implemented at least in part utilizing an MPIO layer, such as an MPIO layer comprising one or more MPIO drivers 112 of the FIG. 1 embodiment or the MPIO layer 332 of the FIG. 3 embodiment, as will now be described in more detail.

In this example algorithm, an MPIO driver of multi-pathing software of a multi-path layer of one or more host devices is configured to swap between multiple available storage access protocols, in a manner that maintains consistent reservation handling across the multiple storage access protocols. Such “swapping” between access protocols is an example of what is more generally referred to herein as “switching” between first and second access protocols, and in some embodiments involves automated seamless migration of at least one logical storage device between the multiple access protocols.

The example algorithm more particularly utilizes one or more MPIO drivers configured to provide device ID management functionality in order to support clustered applications across multiple protocols, such that the management of reservations is independent of the storage access protocol used, thereby ensuring that the clustered application can switch between protocols seamlessly.

Some storage arrays maintain a registration database containing registered initiator-target (I-T) nexus information per logical storage device, and also containing registered keys along with a current device reservation holder. Each such I-T nexus illustratively corresponds to a different path for accessing the logical storage device. This registration database is typically maintained by the storage array on both a per-device and a per-protocol basis, and therefore it is difficult under current practice to handle reservations in environments where the hosts use reservations and a logical storage device is accessed via multiple protocols. For example, in the above-noted case of swapping between SCSI-FC and NVMeF protocols, handling NVMeF reservations is simpler than handling SCSI-FC reservations, because the NVMeF registrations are not managed per I-T nexus. In NVMeF, as part of a connect command, the host will register its host NVMe Qualified Name (NQN) identifier, also referred to as host NQN/ID. The host NQN/ID used as a key in NVMeF replaces the randomly-generated keys used in SCSI. The process of acquiring reservations is similar across both protocols, and is described, for example, in the SCSI and NVMe access protocol specifications.

As will become more apparent, the example algorithm below facilitates management of reservations for a logical storage device independent of the storage access protocol used by a clustered application.

The example algorithm for implementing multiple access protocol reservation handling in the present embodiment includes the following steps:

1. The MPIO driver on a given clustered application host will register on each I-T nexus through which the logical storage device is visible to that host. Each such I-T nexus illustratively corresponds to a different path for accessing the logical storage device of the storage array from the host. It is assumed that these and other portions of the algorithm that are described as being performed by an MPIO driver on one clustered application host are similarly performed by other MPIO drivers on respective other hosts that are executing corresponding instances of the clustered application.

2. The storage array will manage the reservation information in a common or merged table or other data structure regardless of the particular access protocol the commands were received on. This includes registration, reservations, queries, etc. For example, such a merged table for a given host illustratively comprises multi-protocol reservation information 400 maintained in a registration database of the storage array, as previously described in conjunction with the illustrative embodiment of FIG. 4.

3. The storage array is configured to expose two flags to the MPIO driver, illustratively via a vendor unique (VU) SCSI command (e.g., VU mode sense command, VU log sense command, etc.) although other types of VU or non-VU commands could be used. The two flags are maintained by the storage array for reading by the MPIO driver via the VU SCSI command, and include:

(a) a first flag indicating whether or not multi-protocol communication is supported by the storage array; and

(b) a second flag indicating whether or not multi-protocol reservations are supported by the storage array.

4. In conjunction with claiming the logical storage device, the MPIO driver will perform a registration command, illustratively with a “group identifier” or group ID common to all access protocols, also referred to herein as a common host name or host ID, on each of the different protocol paths available to the device:

(a) the MPIO driver illustratively uses a VU registration command (e.g., different than the standard registration command in the SCSI or NVMeF protocols), although other types of VU or non-VU commands could be used;

(b) the MPIO driver will also send the underlying protocol registered key to the storage array with this VU command;

(c) a more particular example of the common host name or host ID is the domain registered host name which is unique and the same regardless of storage access protocol (e.g., SCSI-FC, NVMeF, etc.); and

(d) the storage array will associate the common host name or host ID with each protocol registered key.

5. The given clustered application on the corresponding host will send a Persistent Reserve Out (PRO) register command to a pseudo device (e.g., as it does for other commands) corresponding to the logical storage device. This is an example of an arrangement in which the MPIO driver presents the logical storage device, which may be accessible via different paths associated with different access protocols, as a single pseudo device to one or more higher layers of the host. In an arrangement of this type, an OS of the host sees the logical storage device as the single pseudo device, rather than as separate devices associated with different ones of the first and second access protocols.

6. Upon receiving the PRO register command from the application, the MPIO driver will send the PRO command on all of the paths that the logical storage device is visible on (e.g., it will register on all paths).

7. Upon receiving the PRO register command on a path, the storage array will store the key received on the corresponding I-T nexus in the registration database of the storage array.

8. When paths utilizing a second access protocol are added to the logical storage device (e.g., the device was SCSI-FC and NVME paths were added to the device), the MPIO driver is aware that the device is already registered with some keys and their common host name or host ID. The MPIO driver will send the above-described VU registration command over the second protocol on the new paths. For example, if the logical storage device was previously registered using SCSI-FC, and NVMeF paths were added, the MPIO driver will send the new VU registration command with the same common host name or host ID previously used with the SCSI-FC registration, and with an NVMeF key.

9. The storage array will register the new paths (e.g., add the keys) in the portion of the registration database common to all protocols for the logical storage device.

10. Since multi-protocol co-existence is typically not supported for a given host device, the assumption is that the above-described on-boarding of a second storage access protocol was done for protocol conversion purposes, although other arrangements are possible.

11. After protocol conversion, the clustered application is illustratively kept un-aware of the protocol conversion. It may read one or more reservation keys by issuing a SCSI-FC reservation command (e.g., a SCSI PRI command) to the MPIO driver. The MPIO driver will translate the SCSI-FC reservation command into an NVMeF read keys command and send that command on an NVMeF path.

12. The storage array will respond with the one or more keys and the MPIO driver will then return the one or more keys to the application.

The MPIO driver portions of the above algorithm may be similarly performed by other MPIO drivers on respective other host devices. Such MPIO drivers illustratively form a multi-path layer comprising multi-pathing software of the host devices.

This particular algorithm is presented by way of illustrative example only, and other embodiments can use other types of algorithms to provide the disclosed functionality for multiple access protocol reservation handling.

In some embodiments, in swapping from a currently utilized access protocol to another access protocol, the MPIO driver on a given host device will pause or “freeze” any new IOs to the logical storage device and drain any existing IOs (e.g., allow pending IOs to finish). The MPIO driver will then swap to the other access protocol, and resume or “thaw” new IOs to the logical storage device.

The term “swap” in the context of swapping of access protocols as disclosed herein illustratively has a different technical implementation for different types of host environments. For example, in an ESXi environment, as described previously, the term “swap” illustratively includes vMotion activity between different hosts, each using a different access protocol. For physical environments, such as Linux for example, the term “swap” illustratively includes switching between different path-sets where each path-set uses a different access protocol. These and other swapping arrangements disclosed herein are only examples, and other embodiments can utilize other migration techniques or more generally other types of switching between access protocols.

Also, ESXi, Linux and other host environments are used herein as non-limiting examples only, and the same or similar multiple access protocol reservation handling techniques can be used in a wide variety of other host device environments.

Illustrative embodiments herein provide significant advantages over conventional arrangements in which a host OS is configured to operate with a particular storage access protocol and cannot swap from a current access protocol to another access protocol in a manner that maintains consistent reservation handling across the multiple access protocols.

Again, the above algorithm is presented by way of illustrative example only, and other embodiments can utilize additional or alternative steps. Also certain steps illustrated as being performed serially can instead be performed at least in part in parallel with one another.

Advantageously, illustrative embodiments can non-disruptively transform a storage access protocol for a logical storage device from SCSI to NVMe and vice versa, while maintaining consistent reservation handling across the multiple access protocols.

Additionally or alternatively, some embodiments provide a storage multi-pathing driver supporting more than one storage access protocol for a single managed device.

The particular multiple access protocol reservation handling arrangements described above are presented by way of illustrative example only. Numerous alternative arrangements of these and other features can be used in implementing multiple access protocol reservation handling in other embodiments.

It is apparent from the foregoing that the illustrative embodiments disclosed herein can provide a number of significant advantages relative to conventional arrangements. For example, some embodiments configure host devices comprising respective MPIO drivers to include functionality for multiple access protocol reservation handling for logical storage volumes or other types of logical storage devices.

The disclosed functionality can be implemented using a wide variety of different host devices and storage systems.

It is to be appreciated that the particular advantages described above are associated with particular illustrative embodiments and need not be present in other embodiments. Also, the particular types of information processing system features and functionality as illustrated in the drawings and described above are exemplary only, and numerous other arrangements may be used in other embodiments.

It was noted above that portions of an information processing system as disclosed herein may be implemented using one or more processing platforms. Illustrative embodiments of such platforms will now be described in greater detail. These and other processing platforms may be used to implement at least portions of other information processing systems in other embodiments. A given such processing platform comprises at least one processing device comprising a processor coupled to a memory.

One illustrative embodiment of a processing platform that may be used to implement at least a portion of an information processing system comprises cloud infrastructure including virtual machines implemented using a hypervisor that runs on physical infrastructure. The cloud infrastructure further comprises sets of applications running on respective ones of the virtual machines under the control of the hypervisor. It is also possible to use multiple hypervisors each providing a set of virtual machines using at least one underlying physical machine. Different sets of virtual machines provided by one or more hypervisors may be utilized in configuring multiple instances of various components of the system.

These and other types of cloud infrastructure can be used to provide what is also referred to herein as a multi-tenant environment. One or more system components such as virtual machines, or portions thereof, are illustratively implemented for use by tenants of such a multi-tenant environment.

Cloud infrastructure as disclosed herein can include cloud-based systems such as AWS, GCP and Microsoft Azure. Virtual machines provided in such systems can be used to implement a fast tier or other front-end tier of a multi-tier storage system in illustrative embodiments. A capacity tier or other back-end tier of such a multi-tier storage system can be implemented using one or more object stores such as Amazon S3, GCP Cloud Storage, and Microsoft Azure Blob Storage.

In some embodiments, the cloud infrastructure additionally or alternatively comprises a plurality of containers illustratively implemented using respective operating system kernel control groups of one or more container host devices. For example, a given container of cloud infrastructure illustratively comprises a Docker container or other type of LXC implemented using a kernel control group. The containers may run on virtual machines in a multi-tenant environment, although other arrangements are possible. The containers may be utilized to implement a variety of different types of functionality within the system 100. For example, containers can be used to implement respective compute nodes or storage nodes of a cloud-based system. Again, containers may be used in combination with other virtualization infrastructure such as virtual machines implemented using a hypervisor.

Another illustrative embodiment of a processing platform that may be used to implement at least a portion of an information processing system comprises a plurality of processing devices which communicate with one another over at least one network. The network may comprise any type of network, including by way of example a global computer network such as the Internet, a WAN, a LAN, a satellite network, a telephone or cable network, a cellular network, a wireless network such as a WiFi or WiMAX network, or various portions or combinations of these and other types of networks.

Each processing device of the processing platform comprises a processor coupled to a memory. The processor may comprise a microprocessor, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a graphics processing unit (GPU) or other type of processing circuitry, as well as portions or combinations of such circuitry elements. The memory may comprise random access memory (RAM), read-only memory (ROM), flash memory or other types of memory, in any combination. The memory and other memories disclosed herein should be viewed as illustrative examples of what are more generally referred to as “processor-readable storage media” storing executable program code of one or more software programs.

Articles of manufacture comprising such processor-readable storage media are considered illustrative embodiments. A given such article of manufacture may comprise, for example, a storage array, a storage disk or an integrated circuit containing RAM, ROM, flash memory or other electronic memory, or any of a wide variety of other types of computer program products. The term “article of manufacture” as used herein should be understood to exclude transitory, propagating signals.

Also included in the processing device is network interface circuitry, which is used to interface the processing device with the network and other system components, and may comprise conventional transceivers.

As another example, portions of a given processing platform in some embodiments can comprise converged infrastructure such as VxRail™, VxRack™, VxRack™ FLEX, VxBlock™ or Vblock® converged infrastructure from Dell Technologies.

Again, these particular processing platforms are presented by way of example only, and other embodiments may include additional or alternative processing platforms, as well as numerous distinct processing platforms in any combination, with each such platform comprising one or more computers, servers, storage devices or other processing devices.

It should therefore be understood that in other embodiments different arrangements of additional or alternative elements may be used. At least a subset of these elements may be collectively implemented on a common processing platform, or each such element may be implemented on a separate processing platform.

Also, numerous other arrangements of computers, servers, storage devices or other components are possible in an information processing system as disclosed herein. Such components can communicate with other elements of the information processing system over any type of network or other communication media.

As indicated previously, components of an information processing system as disclosed herein can be implemented at least in part in the form of one or more software programs stored in memory and executed by a processor of a processing device. For example, at least portions of the functionality of host devices 102, network 104 and storage arrays 105 are illustratively implemented in the form of software running on one or more processing devices. As a more particular example, the instances of path selection logic 114 may be implemented at least in part in software, as indicated previously herein.

It should again be emphasized that the above-described embodiments are presented for purposes of illustration only. Many variations and other alternative embodiments may be used. For example, the disclosed techniques are applicable to a wide variety of other types of information processing systems, utilizing other arrangements of host devices, networks, storage systems, storage arrays, storage devices, processors, memories, IO queues, MPIO drivers, path selection logic, migration control logic and additional or alternative components. Also, the particular configurations of system and device elements and associated processing operations illustratively shown in the drawings can be varied in other embodiments. For example, a wide variety of different host device, MPIO driver and storage system configurations and associated multiple access protocol reservation handling arrangements can be used in other embodiments. Moreover, the various assumptions made above in the course of describing the illustrative embodiments should also be viewed as exemplary rather than as requirements or limitations. Numerous other alternative embodiments within the scope of the appended claims will be readily apparent to those skilled in the art. 

What is claimed is:
 1. An apparatus comprising: at least one processing device comprising a processor coupled to a memory; said at least one processing device being configured: to register a logical storage device of a storage system for a first set of paths associated with a first access protocol using a host identifier; to send a first reservation command in the first access protocol over each of the paths in the first set of paths; to register the logical storage device of the storage system for a second set of paths associated with a second access protocol using the same host identifier used in registering the logical storage device for the first set of paths; to receive an additional reservation command in the first access protocol; and responsive to receipt of the additional reservation command in the first access protocol, to translate the additional reservation command to the second access protocol, and to send the additional reservation command in the second access protocol to the storage system.
 2. The apparatus of claim 1 wherein the first access protocol comprises a Small Computer System Interface (SCSI) access protocol and the second access protocol comprises a Non-Volatile Memory Express (NVMe) access protocol
 3. The apparatus of claim 2 wherein the SCSI access protocol comprises a SCSI over Fibre Channel (SCSI-FC) access protocol and the NVMe access protocol comprises an NVMe over Fabrics (NVMeF) access protocol.
 4. The apparatus of claim 1 wherein said at least one processing device comprises at least a portion of at least one host device coupled to a storage system via at least one network.
 5. The apparatus of claim 4 wherein the paths are associated with respective initiator-target pairs and wherein each of a plurality of initiators of the initiator-target pairs comprises a corresponding host bus adaptor of said at least one host device and each of a plurality of targets of the initiator-target pairs comprises a corresponding port of the storage system.
 6. The apparatus of claim 4 wherein said at least one host device comprises a multi-path layer, the multi-path layer comprising at least one multi-path input-output driver configured to control delivery of input-output operations from said at least one host device to the storage system over selected paths through the network.
 7. The apparatus of claim 1 wherein the host identifier comprises a host name of a particular host device.
 8. The apparatus of claim 1 wherein registering the logical storage device for the first set of paths associated with the first access protocol comprises: for each path in the first set of paths: sending a vendor unique registration command to the storage system for the path; and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the first access protocol; wherein the storage system associates the host identifier with the registered keys for the respective paths of the first set of paths.
 9. The apparatus of claim 8 wherein the key type specified in the first access protocol comprises a randomly-generated key.
 10. The apparatus of claim 1 wherein registering the logical storage device for the second set of paths associated with the second access protocol comprises: for each path in the second set of paths: sending a vendor unique registration command to the storage system for the path; and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the second access protocol; wherein the storage system associates the host identifier with the registered keys for the respective paths of the second set of paths.
 11. The apparatus of claim 10 wherein the key type specified in the second access protocol comprises a host identifier.
 12. The apparatus of claim 1 wherein said at least one processing device is further configured: to send a vendor unique sense command to the storage system; and to receive multi-protocol configuration information from the storage system responsive to the vendor unique sense command; wherein the multi-protocol configuration information comprises at least one of: (a) an indication as to whether or not multiple access protocols are supported by the storage system; and (b) an indication as to whether or not multiple access protocols reservations are supported by the storage system.
 13. The apparatus of claim 1 wherein receiving an additional reservation command in the first access protocol comprises receiving a read reservation keys command.
 14. The apparatus of claim 1 wherein said at least one processing device is further configured: to receive from the storage system, in response to the additional reservation command sent to the storage system in the second access protocol, reservation information of a type specified in the second access protocol; and to provide the reservation information to a requesting application.
 15. A computer program product comprising a non-transitory processor-readable storage medium having stored therein program code of one or more software programs, wherein the program code, when executed by at least one processing device comprising a processor coupled to a memory and configured to communicate over a network with a storage system, causes said at least one processing device: to register a logical storage device of a storage system for a first set of paths associated with a first access protocol using a host identifier; to send a first reservation command in the first access protocol over each of the paths in the first set of paths; to register the logical storage device of the storage system for a second set of paths associated with a second access protocol using the same host identifier used in registering the logical storage device for the first set of paths; to receive an additional reservation command in the first access protocol; and responsive to receipt of the additional reservation command in the first access protocol, to translate the additional reservation command to the second access protocol, and to send the additional reservation command in the second access protocol to the storage system.
 16. The computer program product of claim 15 wherein registering the logical storage device for the first set of paths associated with the first access protocol comprises: for each path in the first set of paths: sending a vendor unique registration command to the storage system for the path; and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the first access protocol; wherein the storage system associates the host identifier with the registered keys for the respective paths of the first set of paths.
 17. The computer program product of claim 15 wherein registering the logical storage device for the second set of paths associated with the second access protocol comprises: for each path in the second set of paths: sending a vendor unique registration command to the storage system for the path; and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the second access protocol; wherein the storage system associates the host identifier with the registered keys for the respective paths of the second set of paths.
 18. A method comprising: registering a logical storage device of a storage system for a first set of paths associated with a first access protocol using a host identifier; sending a first reservation command in the first access protocol over each of the paths in the first set of paths; registering the logical storage device of the storage system for a second set of paths associated with a second access protocol using the same host identifier used in registering the logical storage device for the first set of paths; receiving an additional reservation command in the first access protocol; and responsive to receipt of the additional reservation command in the first access protocol, translating the additional reservation command to the second access protocol, and sending the additional reservation command in the second access protocol to the storage system; wherein the method is performed by at least one processing device comprising a processor coupled to a memory.
 19. The method of claim 18 wherein registering the logical storage device for the first set of paths associated with the first access protocol comprises: for each path in the first set of paths: sending a vendor unique registration command to the storage system for the path; and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the first access protocol; wherein the storage system associates the host identifier with the registered keys for the respective paths of the first set of paths.
 20. The method of claim 18 wherein registering the logical storage device for the second set of paths associated with the second access protocol comprises: for each path in the second set of paths: sending a vendor unique registration command to the storage system for the path; and sending a registered key for the path with the vendor unique registration command, the registered key having a key type specified in the second access protocol; wherein the storage system associates the host identifier with the registered keys for the respective paths of the second set of paths. 